1. Field of the Invention
This invention pertains to a muffler particularly adapted for portable internal combustion engines such as used on chain saws and other portable power units.
2. Description of the Prior Art
In internal combustion engines used on portable tools and machines such as chain saws and so called power handles it is necessary to make the muffler for the engine exhaust gas as compact as possible and yet capable of providing suitable sound attenuation without reducing engine performance. Moreover, in portable power tools such as chain saws it is important and necessary that the muffler be arranged on the engine in such a way so as to direct the exhaust gas flow away from the operator and to minimize the chance of the operator being burned by direct contact with the muffler structure.
It is also important to provide mufflers for portable engines which are adapted to minimize the chance of igniting fires from direct contact of the muffler structure with objects or materials normally found in the operating environment of the engine. In this regard it has also been deemed desirable and necessary to insure that the temperature of the exhaust gas flow be reduced as much as possible immediately downstream of the muffler outlet opening.
The aforementioned desired and necessary features of mufflers for portable engine driven tools have been at best only partially obtainable with prior art muffler designs and arrangements. Furthermore, it has been generally accepted practice with heretofore known mufflers for portable internal combustion engines to provide a muffler structure which is a somewhat complex assembly of parts brazed, welded or crimped together into a unitary structure. This approach to muffler design and fabrication is not only expensive but necessitates replacement of the entire muffler structure if any damage is incurred to any portion of the muffler.